Gravitational waves from accretion disks: Turbulence, mode excitation, and prospects for future detectors

We study gravitational-wave emission by turbulent flows in accretion disks around spinning black holes or neutron stars. We aim to understand how turbulence can stochastically excite black hole quasinormal ringing and contribute to a stochastic gravitational-wave background from accretion disks around compact objects. We employ general relativistic magnetohydrodynamic simulations and feed them as the source of the Teukolsky master equation to evaluate the gravitational wave energy spectrum of a single source. The stochastic gravitational wave background from accretion disks generated by the population of stellar-mass compact objects is far below the sensitivity of third-generation ground-based detectors. In contrast, the supermassive black hole population, in particular those actively accreting, could lead to ${\mathrm{\ensuremath{\Omega}}}_{\mathrm{GW}}\ensuremath{\sim}{10}^{\ensuremath{-}15}$ in the microhertz. This signal remains well below the sensitivities of pulsar-timing arrays and LISA, making direct observation infeasible.